This invention relates to a carburetor used for internal combustion engines, and more particularly relates to an idling fuel supplying device of a carburetor having a means for improving the atomization characteristic of liquid fuel exhibited during the idle driving condition of internal combustion engines.
Generally speaking, a carburetor is used as a device for supplying fuel in a gas internal combustion engine which is most widely used as a prime mover of vehicles. Such a carburetor usually consists of a high-speed fuel supplying system (main supplying system) and a low-speed fuel supplying system (slow supplying system). The low-speed fuel supplying system is caused to perform a low-speed operation, a light-loading operation or an idling rotation of an internal combustion engine by supplying a small amount of liquid fuel into an intake passage at the downstream of a throttle valve through an idle port and a slow port when the throttle valve closes, i.e., during an idle driving condition or when the opening of the throttle valve is small, i.e., during the low-speed driving condition.
No special means is provided in the conventional carburetor for improving the atomization characteristic of the liquid fuel being fed into the intake passage during the idle driving condition. Therefore, during the idle driving condition or during the low-speed driving condition, since the opening of the throttle valve is small, a part of the air sucked into the intake passage flows downwardly in the downstream side of the throttle valve to generate a vortex flow. When fine grains of liquid fuel injected from the idle port are absorbed by the downstream area and come into contact with the downstream side wall of the throttle valve, these fine grains agglomerate on the wall to become larger fuel grains which are then sucked, without any changes in form, into combustion chambers of the engine. Otherwise, the liquid fuel grains are caught on the inner wall of the intake passage and caused to flow into the combustion chambers along the inner wall of the intake passage in the state of a liquid membrane. Therefore, during the idle driving condition, the atomization characteristic of the liquid fuel is not effective and a uniform air and fuel mixture cannot be obtained. Due to these negative factors, the combustion characteristic, the stability in the revolutions of the engine and the fuel consumption of the internal combustion engine are also negatively affected. In addition, poisonous combustible substances, such as hydrocarbons (HC), carbon monoxides (CO) and the like, are contained in the exhaust gas.